They correspond to the percentage of your maximum heart rate. Generally speaking, the higher the heart rate, the stronger the burn.

Dave Wright puts it simply, "You will burn more calories the higher your effort, but that depends on whether your body is working efficiently." Essentially, you need to be able to maintain the state.

This is, of course, the basis of HIIT training, for which you want to be working at 80% and above during your 'on' periods.

However, you should also remember the importance of LISS, during which your heart rate will be around 50%-60% as it burns the fat you've already got, rather than the calories you've eaten that day.

Fitbit (Ionic, £219.99) describes the area around 60% as their 'fat burn' zone, "this is where you will be targeting your aerobic endurance, with a large proportion of the energy coming from fats as a fuel source."

Fitbit

Advertisement - Continue Reading Below

For toning up

Monitor: Your varying heart rate zones

So you want to tone up. One way to do this is to educate yourself on your VO2 max and start building up your cardio fitness, and to do this, learning to become familiar with your different heart rate zones can be helpful.

Why? Well, to improve your cardiovascular fitness, you need to be in your peak zone for as long as possible.It's not easy, as Wright reminds us: "To change your body so that it doesn’t acclimatise to certain thresholds you need to keep increasing how hard your heart can work."

For hitting daily movement goals

Monitor: Your steps

If you're looking for something to track your daily activity generally, a fitness tracker, to state the obvious, can do this for you.

However, it is important to remember that the calorie count on any piece of tech will be based on a generalised equation. Researchers at Iowa State University did a study of various trackers and found the best still had an error rating of 9% when it came to calories.

That said, it's important you give the kit whatever information you have, like your height, weight and age to ensure it's as accurate as possible. Remember, as your body changes, so too should the settings on your device. Even losing a few pounds can have a knock-on effect on your daily activity and calorie intake recommendations, which so many people forget.

Advertisement - Continue Reading Below

Advertisement - Continue Reading Below

For losing fat

Monitor: Your calorie intake

If you're using your fitness tracker to monitor your calorie intake, most important thing to remember about calories and losing weight is deficit. You're not going to lose weight if you're not burning off more than you consume.

Some fitness trackers like the Fitbit can be integrated with apps like MyFitnessPal which count your calories.

Before you start comparing you need to understand your Resting Metabolic Rate. Essentially this is how many calories you need to stay alive with no activity. Don't worry about to doing loads of maths as there are plenty of tools online that can work it out for you. This one on bodybuilding.com is quick and easy to use.

Once you have your RMR you can compare this with how many calories you've eaten. Make sure you take your workouts into account, for example, if your RMR is 1600 calories, you burned 400 through activity then technically you could consume 2,000 calories and maintain the same weight.

But to be in a calorie deficit you'd probably want to consume around 1600-1800 calories.

You can either track this every day or try comparing your weekly burn with your weekly calorie intake. Many trackers will send you a weekly report if you ask them to in the settings.

And what's more, you can also look back on days and consider when you ate more and what triggered it.

Advertisement - Continue Reading Below

Remember to compare your burn with your calorie intake. However, unlike when you're aiming to lose weight, you need to remember that food is fuel.

Take a look at the days when you've done intense exercise and check whether you gave yourself enough food to go on or recover with.

It can be helpful to keep a diary of how workouts feel so you can consider this as well, that way you can discover what you personally need to excel at your workout.

Just remember, HIIT class on an empty stomach isn't necessarily the way to build up your fitness.

If you're an avid gym-goer who gets frustrated at the disparage between your fitness tracker and your workout equipment, you're in for a treat. A recent Apple update includes a 'Gym Kit' feature, which allows you to sync certain machines, like treadmills and exercise bikes, to your watch for better, more accurate workout statistics. Result.

For tracking your sleep

Monitor: Your hours of NREM sleep

When it comes to sleep, fitness trackers can be more of an annoying reminder than anything all that helpful. Googling 'Why am I tired all the time?'. Stop.

Whyte explains: "Optimising sleep (non-rapid eye movement, or NREM deep sleep) duration and quality is critical to enhancing recovery and adaptation from exercise. You should aim to reduce the number of awake and restless periods. Your aim is to maximise the period of deep sleep during the night."

So far, so fairly obvious.

However, what you can learn are the triggers for better or worse sleep, which in turn, can help you figure out how to fall asleep fast. That's why the data only really becomes useful when taken over a decent length of time.

As you build up a picture, you can identify days when you had better or worse sleep and why that may be.

Women's Health, Part of the Hearst UK Wellbeing Network
Women's Health participates in various affiliate marketing programs, which means we may get paid commissions on editorially chosen products purchased through our links to retailer sites.